Sitting For Long Periods May Harm The Heart, New Study Finds

Most people have no doubt heard that sitting is the new smoking—sedentarism is linked to all kinds of undesirable outcomes, like cancer, thinning of certain brain regions, and mortality. It’s also linked to heart disease, and a new study from the University of California, San Diego confirms the connection in aging women. Not only does the total amount of sedentary time seem to confer heart risk over the years, but the length of each bout of sitting also seems to matter. The bottom line is as it has been: Get up and move as often as you can.

The researchers, who published in the journal Circulation, studied a group of 5,000 racially diverse women who were 63-97 years old. They gave the participants accelerometers to wear for up to a week, to track their active vs. sedentary time. This method is an advantage since many studies rely on participants’ recall of how their time is spent, which may or may not be accurate. They tracked the women for five years, taking note of their cardiovascular risk, including heart attack, stroke, heart pains requiring hospitalization, and death from heart disease.

They found that, as expected, women who spent more time being sedentary had an increased likelihood of heart disease. And the longer the bout of sedentary behavior, the greater the risk.

“Each additional hour of sedentary time, on average,” the authors write in their paper, “was associated with a 12% increase in multivariable adjusted risk for CVD. Dose-dependent increased risk of 4% was also observed for each 1-minute increase in sedentary bout duration, indicating that prolonged sedentary accumulation patterns are associated with higher CVD risk in older women.”

In other words, for each additional unit of time a woman spends sitting, her risk of heart disease rises. The authors conclude that “both sedentary time and the way in which it is accumulated may be relevant for cardiovascular health in older women.”

Sadly, exercise did not fully dissolve the risk of sitting, as previous studies have also found.

"Higher amounts of sedentary time and longer sedentary bouts were directly associated with cardiovascular disease," said study author John Bellettiere, said in a statement. "Importantly, the association showed up regardless of a woman's overall health, physical function, and other cardiovascular risk factors, including whether they also were engaging in moderate to vigorous physical activity."

So if you sit at a desk all day, working out after work and on the weekends may not undo the damage accrued by sitting.

As always, these findings aren’t causal, they’re correlation. But because the connection held when the researchers controlled for various other factors, it’s likely that the one may lead to the other. And there are several mechanisms that might explain it. Among them, the authors suggest, is the possibility that lower energy expenditure reduces skeletal muscle movement and blood flow, which themselves contribute to problems metabolizing glucose. Additionally, when people don’t move much, blood vessel function is impaired and reactive oxygen species, which can wreak havoc on cells (including heart cells), can form.

The authors of course suggest reducing sedentary time, perhaps not all at once, but little by little. “For example,” they write, “a one-hour reduction in sedentary time could reduce CVD risk by 12% for women who are typically sedentary for 8 hours/day as well as for women who are typically sedentary for 12 hours/day.” And though the study was done in older women, it likely applies to everyone, as behaviors affecting health often add up over the course of a lifetime.

For those who spend long hours in a seat, punctuating this time with rising and moving around may break the pattern enough to reduce some of the negative effects. And if all else fails, fidget—moving around a bit while you sit seems to partially reduce the mortality risk that comes from being still. In any case, the new study provides some nice evidence that spending the majority of the day sitting is one of our modern-day behaviors that may need serious reconsideration.